Go to ACP > Templates & Style > Templates > Search/Replace > do a name search for anything that will have a result. Choose a result, and click the name of it. Edit it, and save. Then, go to Go to ACP > Templates & Style > Templates > Search/Replace again, do the same name search, and you'll see the template name in the Global Templates; you can then delete this, meaning there is no version of that template anywhere, so it just loads a blank page (or blank area) when you go to the page that would load that template.

This happens because when you get the results of the search, you're not clicking Options to choose the template set. IMO the template name should be unclickable, forcing you to click Options and choose a template set.